For many businesses, the need to keep certain equipment operating is critical to the success of the business, and the loss of electrical power can be devastating. Accordingly, many such businesses plan for ensuring a continuous supply of electrical power. However, known methods commonly used for ensuring a continuous supply of electrical power can be relatively expensive to employ and maintain.
The power supply system for a particular application may include an Uninterruptible Power Supply (UPS) that utilizes battery back-up and redundancy to supply virtually continuous power to the equipment. However, such a system typically has a relatively high front-end cost and generally requires substantial maintenance.
As an alternative, the power supply system may include two separate utility feeds from different distribution points. The power supply system may also include two separate AC to DC power converters. One AC to DC power converter may be connected to one utility feed, and the other AC to DC power converter may be connected to the other utility feed. For many applications, the performance of such a system is generally acceptable because the risk of the simultaneous loss of the two separate utility feeds is relatively low. Although this approach is more economical than utilizing an Uninterruptible Power Supply, the overall cost associated with such a system is still relatively high because of the need for the two separate AC to DC power converters.
In one general respect, the present invention is directed to a dual input power converter. According to one embodiment, the dual input power converter includes a transformer having a first and second primary windings and a secondary winding. The converter further includes a first primary circuit for coupling a first power source to the first primary winding, and a second primary circuit for coupling a second power source to the second primary winding. In addition, the converter may include a secondary circuit connected to the secondary winding for rectifying a voltage across the secondary winding. Further, the converter may include a control circuit coupled to the first and second primary circuits for controlling the first and second primary circuits. The control circuit may control the first and second primary circuits such that the first and second primary circuits cyclically couple the first and second power sources, respectively, to the transformer at a common frequency in an interleaved mode such that, during a switching cycle, the first primary circuit couples the first power source to the transformer during a first interval of the switching cycle and the second primary circuit couples the second power source to the transformer during a second, subsequent interval of the switching cycle. Additionally, according to another embodiment, the control circuit may control the first primary circuit to couple the first power source to the transformer at twice the common frequency when the second power source fails. According to other embodiments, the power converter may further include current sense transformers in series with the first and second primary windings. In addition, according to other embodiments, the primary circuits may include one or two switching devices for coupling the input power sources to the primary windings.